JPS6056274B2 - Laser ignition device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laser ignition device that ignites an engine using a shear acid pulse of a semiconductor laser.

Typical ignition systems for conventional 4-cylinder engines include:
(n) Published by Sankaido "Internal Combustion Engine" 18on No. 9 (197shi 9
It is well known as shown in the 45th Tribute (Month issue).

FIG. 1 shows this ignition system. In this ignition system, a current flowing from a battery 2 to the primary side of an ignition coil 3 is intermittent by a contact point 1 that turns on and off in synchronization with the engine rotation. A high voltage pulse with a peak value of -20KV to -25KV is generated on the next side. This high-pressure pulse is distributed to high-tension cords 5a, 5b, 5c, and 5d with resistance by a rotary distributor 4 in synchronization with the contact point 1, and is transmitted to the spark plug 6 of each cylinder via the high-tension cord.
a (1 cylinder), 6b (3 cylinders), 6c (4 cylinders), 6d
(2 cylinders) sequentially. The waveform of the high-voltage pulse Vs supplied to each spark plug (high-voltage pulses Vsl, Vs2, Vs3, and Vs4 are applied to the plugs 6a, 6b, 6c, and 6d, respectively) is as shown in Figure 2, and its peak The value vp (capacitive discharge voltage) can be -15 to -20 KV.
When the high-voltage pulse Vs supplied to each spark plug increases and reaches the peak value Vp, the discharge of the spark plug and the air-fuel mixture between the electrodes causes dielectric breakdown and the electric charge accumulated in the high tension cord causes dielectric breakdown. A capacitive discharge occurs between the spark plug and the spark plug.
Next, in response to the supply of inductive energy from the ignition coil 3, the inductive discharge of the discharge voltage V1 is approximately -O, 5F (V).
Lasts for about TT1S. Sparks accompanying these discharges reliably ignite and burn the air-fuel mixture. In such an ignition device, ignition is reliably performed with a relatively simple configuration, but it takes -20% to obtain the energy necessary for ignition.
A high-voltage pulse with a peak value of around KV is periodically generated, and a discharge is generated between the discharge electrodes of the spark plug and between the rotor and the side electrodes of the distributor. When the electric charge accumulated near the electrode is instantaneously discharged, an impulse current L1 with a peak value of 10 amperes and a pulse width of several nanoseconds flows near the electrode.

At this time, the ignition plug receives an impulse current 1 with a peak value h of -80 to -100 A and a pulse width of several nanoseconds as shown in Figure 2.
s (impact current 1S1 for plugs 6a, 6b, 6c96d)
91S291s391s4) flows. Since this impulse current L has a wide frequency spectrum ranging from several megahertz to several hundred megahertz, it is radiated into the air as electromagnetic waves from the ignition circuit connected to the distributor and spark plug, and becomes radio wave noise over a wide range of various communication devices. The problem is that it affects. Therefore, in order to solve the problem of such noise,
No. 532 uses laser light.

We have proposed an ignition device that guides laser light to the ignition part of each cylinder through an optical waveguide and ignites it sequentially. Incidentally, ignition of an engine requires an output of at least several kilowatts, but conventionally,
As a means to generate a pulsed laser with this level of output, a giant pulse generator is used that drives a YAG laser or a CO2 laser (each of which has dimensions of several tens of centimeters in length, width, and depth) using a Q switch. , small electric j
It is about the size of a small microwave oven and is not suitable for wheels. The present invention has been made in view of the above points, and an object of the present invention is to provide an ignition device having a compact high-output laser suitable for use in a vehicle. ! , an XX inverter that boosts the power supply pressure, a capacitor that is connected in parallel with the semiconductor laser and is charged by the output of the It is composed of semiconductor switching elements that turn on and off in synchronization with the The present invention will be explained below with reference to FIGS. 3 to 13.

FIG. 3 shows the overall configuration of an embodiment of the laser ignition device according to the present invention.

The ignition command signal from the ignition timing control circuit 10 that detects the ignition timing of the engine is input to the pulse drive circuit 20, and the semiconductor laser generator 30 is pulse-modulated using a high voltage source, with a pulse width of 10 microseconds. A giant pulse laser beam with a peak value of several 10 kilowatts is generated. This laser beam is focused on the open end P of the optical fiber F by the lens 40 and is injected into the optical fiber F. ) giant pulse ● The laser is transmitted to the optical splitter 50 by the optical fiber F, and the optical fibers Fl, F2, F3, F, according to the instructions of the distribution control signal output from the ignition timing control circuit 10.
distributed to. Giant Pulse The laser is sequentially supplied to the condenser 70 of the 1st to 4th cylinders of the engine 60 (in the order of 1st → 3rd → 4th → 2nd cylinder) through optical fibers F1 to F, and the air-fuel mixture in the combustion chamber is ignite and burn. The optical fiber must be able to transmit a giant pulse laser with a peak value of several 10 kilowatts at low loss without dielectric breakdown, and a quartz fiber with a core of 2.0% is used. Next, the operation of each part will be explained in detail.

(1) Operation of the ignition timing control circuit and optical distributor FIG. 4 shows the detailed circuit configuration of the ignition timing control circuit 10 and the optical distributor 50, and FIG. 5 shows each part of FIGS. 3 and 4. The signal waveform at is shown.

Now, in Fig. 4, a resistor R is connected in series with the contact point 11, which turns on and off in synchronization with the rotation of the engine. and connect it to the battery 12. The output of contact point 11 is connected to a constant voltage diode ZD with a Zener voltage of 5V.
A pulse signal S1 is obtained which is stabilized at , and changes in synchronization with the rotation of the engine. In addition, in Figure 5, the engine rotation is 1500.
An example of r''Pm is shown below. This pulse signal S1 is input to the monostable multivibrator 13a having a metastable time of 2 milliseconds, and at the falling time of the monostable multivibrator 13a, a pulse signal S2 with a pulse width of 2 milliseconds is generated. A pulse signal S3 divided by 112 and a pulse signal S4 divided by 114 are generated by supplying the signal to the binary counter 14.These two pulse signals S3 and S4 are called distribution control signals.On the other hand, the pulse signal S1 is supplied to the quasi-stable time. A pulse width of 50 microseconds is input to the monostable multivibrator 13b having a pulse width of 50 microseconds.
A microsecond pulse signal ■ is generated, this signal S5 is applied to a monostable multivibrator 13c having a metastable constant time of 10 microseconds, and a pulse width of 10 microseconds is generated at the falling time of the signal S5.
A microsecond ignition command signal S6 is obtained. Next, the distribution control signals S3 and S4 are guided to the optical splitter 50, and the distribution control signals S
3 is input to the switch drive circuits 51 and 52, and the front and rear edges of the pulses drive the optical switches 53 and 54 using differential signals S7 and S8 (the voltages of the two signals
The optical transmission path of the optical switches 53 and 54 is switched from the output terminal n1 to N2 at the leading edge of the distribution control discharge S3, and the same signal Connect the output end from N2 to n1 at the trailing edge of S3.
Switch to

Further, the distribution control signal S4 is input to the switch drive circuit 55, and the front and rear edges of the pulse generate a differential signal S9 (Vdl-Vd2) that drives the optical switch 56.
The output terminal of the optical transmission path No. 6 is switched from n1 to N2 at the leading edge of the distribution control signal S4, and the output terminal is switched from N2 to n1 at the trailing edge of the same signal. The ignition command signal S6 is input to the pulse drive circuit 20, which pulse-modulates the semiconductor laser generator 30 to obtain a giant pulse laser SlO.
This giant pulse ● laser is transmitted to the input terminal m of the optical switch 56 through the optical fiber F. (a) In FIG. 5, during the period T1, the giant pulse
The signal is sent to the optical fiber F5 via a route from the input terminal m to the output terminal n1 of the optical switch 53, and is further transmitted to the optical fiber F1 via a route from the input terminal m to the output terminal n1 of the optical switch 53, and is supplied to one cylinder as Sll.

(b) During the period of time T2, the giant pulse laser SlO is connected from the input terminal m to the output terminal n of the optical switch 56.
The signal is transmitted to the optical fiber F5 via a route from the input terminal m of the optical switch 53 to the output terminal N2, and further transmitted to the optical fiber F2 via a route from the input terminal m of the optical switch 53 to the output terminal N2, and then transmitted to the three cylinders as Sl2.

(c) During the period T3, the giant pulse laser SlO is connected from the input terminal m of the optical switch 56 to the output terminal N.
The signal is sent to the optical fiber F6 via a route from the input terminal m to the output terminal n1 of the optical switch 54, and is further transmitted to the optical fiber F3 via a route from the input terminal m to the output terminal n1 of the optical switch 54, and is supplied to the four cylinders as Sl3.

(D) During the period T4, the giant pulse laser SlO is connected from the input terminal m of the optical switch 56 to the output terminal N.
The signal is sent to the optical fiber F6 via a route from the input terminal m to the output terminal N2 of the optical switch 54, and is further transmitted to the optical fiber F4 via a route from the input terminal m of the optical switch 54 to the output terminal N2, and is supplied to the two cylinders as Sl4.

In this way, the giant pulse laser SlO sequentially connects optical fibers 1, F2, F3 in synchronization with the rotation of the engine.
, F4, and is supplied to each cylinder of the engine in the order of \1 cylinder → 3 cylinder → 4 cylinder → 2 cylinder.

The waveforms of the diamond pulse lasers transmitted on the optical fibers F1 to F4 are shown at Sll to S14 in FIG. )) Operation of switch drive circuit and optical switch f)
The detailed circuit configuration of the switch drive circuit shown in FIG. 4 and signal waveforms at each part are shown in FIGS. 6 and 7.

Since the switch drive circuits 51, 52, and 55 have the same configuration, the switch drive circuit 51 will be explained. Distribution control signal S
3 is input, a pulse signal Sl5 with a pulse width of 7 milliseconds is generated, which drives the monostable multivibrator 51a having a metastable time of 7 milliseconds at its leading edge.

When the pulse signal Sl5 is at H (High) level, the transistor Q1 is conductive, its collector voltage V1 is 4V lower than the power supply voltage, and the emitter voltage V2 is 4V lower than the ground potential.
To increase. Therefore, transistors Q2 and Q3 conduct, their output ■d1 becomes +24 volts, their output ■D2 becomes 0 volts, and the differential signal S7 (■d1 - ■D2) becomes +24 volts.
Becomes a bolt. At this time, a current 1 = 100 milliamperes flows through the coil L2 wound around the core 56a of the optical switch 56 and the coil L2 wound around the core 56b.
6b is excited, and the permanent magnet 56d equipped with the parallelogram prism 56c is attracted to the core 56a and repelled by the core 56b, and moves in the A direction. At this time, the optical transmission path is switched from the output terminal n1 to N2 with a response as shown in FIG. Similarly, at the trailing edge of the distribution control signal S3, the metastable time 7
The monostable multivibrator 51b having a millisecond pulse width is driven to generate a pulse signal Sl6 with a pulse width of 7 milliseconds.

When the pulse signal Sl6 becomes H level, the transistor Q4
changes from a non-conducting state to a conducting state, and its emitter voltage V
4 increases from O volts to 4 volts, and the collector voltage V3 decreases from the power supply voltage 24 volts to 20 volts. Therefore, transistors Q5 and Q6 are conductive, output Vdl is 0 volts, and output ■6. becomes +24 volts, and the differential signal 11
(■d1-Vd9) becomes -24V and the optical switch 56
A current 1=-100n1A flows through the coils L1 and L2 in the opposite direction to that in the above case, and the cores 56a and 56b are excited with the opposite polarity to that in the above case. Therefore, the permanent magnet 5
6d is repelled by the core 56a and is attracted to the core 56b, resulting in B
direction, and the optical transmission path is switched from the output terminal f to the output terminal n1 with responsiveness as shown in FIG. (b) Next, the operation of the optical switch will be explained.

The detailed circuit configuration of the optical switch shown in FIG.
As shown in the figure.

Since the optical switches 53, 54, and 56 have the same configuration, the optical switch 56 will be explained. The optical switch 56 is a movable prism type with low loss and high responsiveness using electromagnetic control, such as NECOD875O (IEICE technical research report MW7).
8-107). The optical switch 56 is sealed with a case 56e to block external light leakage and laser light leakage, and connects an input optical fiber F and two optical fibers F5 and F.
6 through connectors 56f, 56g, and 56h. Further, the laser beam inputted from the optical fiber F passes through the connector 56f, is converted into parallel light by the Selfox lens 56i, and is incident on the parallelogram prism 56c when it is at the position C shown by the solid line, as shown in FIG. The light travels along an optical path as shown by a solid line and is guided to a triangular prism 56j. Therefore, the laser beam is returned in the opposite direction by the prism 56j, enters the Selfox lens 56k, and is sent to the optical fiber F6 through the connector 56h. On the other hand, the parallelogram prism 56c is at a position D indicated by a broken line.
, the incident laser light travels straight along the optical path shown by the broken line and enters the triangular prism 561.
The light is returned in the opposite direction, enters the SELFOC lens 56m, and is sent to the optical fiber F5 through the connector 56g. (
3) Operation of pulse drive circuit and semiconductor laser (a)
Description of the pulse drive circuit shown in FIG. 3 FIG. 9 shows the detailed circuit configuration of the pulse drive circuit, and FIG. 10 shows signal waveforms at various parts.

Note that FIG. 10 shows an enlarged view of the time TA and TB in FIG. When the ignition command signal S6 is applied to the inverter 21 and its polarity is reversed, the base voltage V. is -0.8 when the ignition command signal S6 is at H level.
volts, causing transistor Q7 to go from non-conducting to conducting. At this time, the collector voltage of the transistor Q7, that is, the gate-source voltage VO of the high-voltage, high-power FET Q8 changes from -Vb to O volts. On the other hand, the voltage of 12 volts of the battery 22 mentioned above is applied to the inverter 23 and boosted to output a DC voltage of +800 volts. Since a capacitor C with a capacitance of 5 microfarads is connected to the output terminal of the inverter 23, the voltage between its terminals is V. varies depending on the load situation. The load of the capacitor C is a semiconductor laser generator 30 configured by connecting m laser diodes LD in series and connecting them in n columns in parallel, and a current 1 flowing through the semiconductor laser generator 30.
A high-voltage, high-power FET Q8 (which may be a thyristor or a high-voltage, high-power transistor) is connected in series. Now, if the voltage -Vp is set lower than the pinch-off voltage -Vp of FETQ8, FETQ8 is normally in a cutoff state, and only while the ignition command signal S6 is at the H level, Vcs becomes O volts, and FETQ8 becomes conductive.

When FETQ8 conducts, a saturation current of 1 flows between the drain and source of FETQ8, regardless of the voltage between the drain and source.
. ss flows. The current 1 flowing through the semiconductor laser generator 30 flows for 10 microseconds when the ignition command signal S6 is at H level as shown in FIG. The accumulated charge is discharged at a constant current of 1=200A, resulting in a voltage between its terminals. decreases from +800 volts to +400 volts. Therefore, the voltage between the terminals of the semiconductor laser generator 30 changes from 0 volts to 400 volts during the 10 microsecond period when the ignition command signal S6 is at the H level, and the power applied to the semiconductor laser generator 30 during this period becomes approximately 80 KW. The semiconductor laser generator 30 consisting of Mxn laser diodes LD has a total output P. = Emit laser light of several tens of kilowatts. Note that the ■-■ inverter 23 is the voltage between the terminals of the capacitor C. It is assumed that the battery has a charging capacity that can increase the voltage from +400 volts to +800 volts in a few milliseconds. (b) Operation of semiconductor laser generator The fine structure of the semiconductor laser generator 30 is shown in FIG.

Its structure consists of a laser diode chip 32 having the structure shown in FIG. 12 mounted on a copper heat sink 31.
n pieces (m pieces electrically connected in series and n rows electrically connected in parallel) are stacked. An insulator 33 made of a beryllia magnet with good thermal conductivity is attached to the upper left of the copper heat sink 31, and a positive electrode lead 34 is fixed on top of the insulator 33. From this lead 34, the striped positive electrodes of the laser diode chips 32 in each row are connected. 32a with a gold wire 35 for electrical connection. Further, a negative electrode lead 36 is attached to the upper right of the copper heat sink 31. When a high voltage pulse (approximately 400 volts) is applied between the positive electrode lead 34 and the negative electrode lead 36 and the aforementioned pulsed current 1 (approximately 200 amperes) flows, from the cleavage plane 32b of each laser diode chip 32. A laser beam L is emitted. The laser diode chip 32 has a size of 100μ as shown in FIG.
It is a GaAs crystal with a size of about 300μ, and its surface has a striped positive electrode 32a with a width of 20μ, and the back surface has a negative electrode 32.
c is formed.

Moreover, its structure is AeGa. It has an As double heterostructure, and the active layer 32d of Ga and As with a thickness of about 0.3μ is sandwiched between AfGaAs crystals with different refractive indexes, so the generated light is confined and has a high Luminous efficiency can be obtained. Note that the laser beam L is a GaA laser beam L at the cleavage plane 32b of the laser diode chip 32.
The radiation is emitted from the vicinity directly below the striped positive electrode 32a of the active layer 32d. (4) Operation of the laser condenser installed in the cylinder Figure 13 shows the laser condenser 70 (see Figure 3)
Shows how it is installed on the cylinder head.

The illustrated cylinder has a well-known structure, and has a hemispherical combustion chamber 71 inside, an intake valve 72 and an exhaust valve 73 are provided diagonally above the combustion chamber 71, and a piston 74 is provided inside the cylinder.
moves up and down.

The laser focusing device 70 includes quartz fibers such as optical fibers F1 to F4 attached to the top of a substantially circular fiber-shaped space 76 formed in a cylinder head 75, and a convex lens 77 fixed near the bottom of the space 76. (For example, focal length 50T
SR), a quartz glass window fitted into the lower end of the space 76 (
For example, the thickness is 10T! Rln with a diameter of 30wn) 78. To explain the operation of the laser condenser 70, the peak value number 10KW1 pulse width 10 is emitted from the spherically processed tips of the optical fibers F1 to F4 having a highly heat-resistant coating attached to the center of the cylinder head 75. A microsecond giant pulse laser SlO is emitted to form a laser beam L with a focal length of 40 to 6-
The laser beam L is focused by a lens 77 in the combustion chamber 71 and passes through a quartz glass window 78 with a thickness of 10 mm and a diameter of 30 to 4 mm provided at the upper end of the combustion chamber 71 to the focal point R of the lens 77 in the combustion chamber 71. Concentrate your energy. The energy of several hundred millijoules from the Giant Pulse Laser SlO causes ionization and dielectric breakdown of the compressed air-fuel mixture, and plasma is instantaneously generated to ignite and burn the air-fuel mixture. As explained above, in the present invention, a semiconductor laser is used as a light source, and a DC-DC inverter and a capacitor are connected, and the electrical energy stored in the capacitor is instantaneously injected into the semiconductor laser using a high-power semiconductor switching element. With this configuration, the semiconductor laser generating section is extremely miniaturized, making it suitable for mounting on a vehicle.

According to this embodiment, if a semiconductor laser generator is used to generate a giant pulse laser, pulse modulation is performed using high voltage and high energy charged in a capacitor, so CO2 laser, ruby laser, YAG laser, etc. Compared to the case of using a gas laser or solid-state laser, the power supply efficiency for generating a giant pulse laser is extremely high, and at the same time, the configuration of the power supply device is simple.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a schematic circuit diagram of a conventional ignition system, Fig. 2 is a voltage and current waveform diagram of a spark plug of the conventional ignition system, and Fig. 3 is a block diagram showing a schematic diagram of a laser ignition system according to the present invention. 4 is a detailed circuit configuration diagram of the ignition timing control circuit and optical spectrometer shown in FIG. 3, FIG. 5 is a signal waveform diagram at each part of the circuit shown in FIG. 4, and FIG. A detailed circuit configuration diagram of the switch drive circuit shown in the figure, FIG. 7 is a signal waveform diagram at each part of the switch drive circuit shown in FIG. 6, and FIG. 8 is a structure of an embodiment of the optical switch used in the present invention. 9 is a detailed circuit configuration diagram of the pulse drive circuit shown in FIG. 3, FIG. 10 is a signal waveform diagram at each part of the pulse drive circuit, and FIG. 11 is a diagram of the semiconductor laser used in the present invention. 12 is a perspective view showing the structure of an LD chip as a component of the semiconductor laser shown in FIG. 11; FIG. 13 is a perspective view showing the structure of the ignition device according to the present invention. FIG. 3 is a schematic cross-sectional view showing the container in relation to the cylinder. 1...Contact point, 2...Battery, 3
...Ignition coil, 4...Distributor, 5a-5d...High tension cord, 6a
~6d... Spark plug, 10... Ignition timing control circuit, 20... Pulse drive circuit, 30... Semiconductor laser generator, 40... Luns, 50... Optical distributor, 60...
...Engine, 70...Luther condenser, L, Ll~!・
...Optical fiber.

Claims (1)

[Claims] 1. A semiconductor laser generator generates a giant pulse laser in synchronization with the ignition timing of the engine, and distributes the giant pulse laser to each cylinder of the engine in a predetermined order via an optical transmission means. In the laser type ignition device for igniting the ignition device, the semiconductor laser generator includes a semiconductor laser, a DC-DC inverter that boosts a power supply voltage, and a semiconductor laser connected in parallel with the semiconductor laser and charged by the output of the DC-DC inverter. A laser ignition device comprising: a capacitor that stores high voltage and high energy; and a semiconductor switching element that is connected in series with the semiconductor laser and turns on and off in synchronization with the ignition timing of the engine. 2. The semiconductor laser according to claim 1, wherein the semiconductor laser is composed of a plurality of laser diodes, and the laser diode has a stacked structure in which a plurality of chips are connected in series and in parallel. Laser ignition device.